We will focus on two major areas concerning the mitogenic stimulation of lymphocytes by some lectins and the lack of stimulation by others. First, we will attempt to determine whether there are classes of receptors for mitogenic and nonmitogenic lectins by a) attempting to isolate receptors directly from the lymphocyte plasma membrane, and b) following the relative movements of receptors about the cell surface using fluorescent tagged lectins. Receptors will be isolated from purified lymphocyte plasma membranes by solubilization of the membranes with detergents followed by affinity chromatography with insolubilized lectin columns. A group of pure lectins will be tagged with different fluorochromes and cells reacted sequentially with the lectins under conditions where receptor migration is favored or inhibited. By following the relative migration of lectin receptors, it should be possible to identify common receptors for various lectin. Secondly, we will attempt to synchronize mammalian lymphocytes in culture. This will be done by incubating lymphyocytes with mitogenic lectins in the presence of certain reversible metabolic blocking agents and then removing the blocking agent. If this succeeds, we will follow several metabolic events which we suspect are involved in mitogenesis and establish their sequence. BIBLIOGRAPHIC REFERENCES: Ahmann, G.B. and Sage H.J.: Stimulation of Guinea Pig Lymphocytes by LcL-A and by LcL-B. Stimulation by Insolubilized LcL-A and Effect of Erythrocytes, and Peritoneal Macrophages on Stimulation by Soluble LcL-A. Presence of a Lymphokine in Culture Fluids of LcL-A-Stimulated Cells. Cell. Immunol. 10, 183 (1974). Ahmann, G.B. and Sage, H.J.: Binding of Purified Lectins to Guinea Pig Lymphocytes. Studies of the Number, Binding Constant and Distribution of Lens culinaris Lectin A and Agaricus bisporus Lectin Molecules on Lymphocyte Surfaces. Cell. Immunol. 13, 407 (1974).